Macroeconomics issue about the definition of " interest rate"
I am preparing the AP macroeconomics exam, but I am confused about the the definition of " interest rate" . I think the definition of " interest rate" should be "An interest rate is the rate at which interest is paid by borrowers for the use of money that they borrow from a lender" ( quoted from Wikipedia) ; however, the meaning of " interest rate" seems to be different from the above when I read the below paragraph about international trade.
In capital markets, if another nation’s interest rate (return on investment) is higher than the domestic interest rate, some people will choose to invest in the other nation’s securities. When consumers import more products from a country or invest in that country’s securities, their demand for that currency increases. This increase in demand pushes the price of the currency higher, so their currency appreciates (rises in value).
the meaning of " interest rate" is "return on investment".
WHY? why this difference happens?